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Cardiovascular and pulmonary
systems
Revision for Unit 1
Tissues, organs, blood vessels, heart,
lungs, exercise physiology
10.6, 10.7 and 10.8
10.7 gas exchange
• Fick’s Law
Rate of diffusion = surface area x concentration difference
thickness of exchange surface
•
•
•
•
to maximise diffusion:
maximise surface area
maximise concentration difference
minimise thickness of exchange surface
10.7
• Human (mammalian) lung:
• maximum surface area
• many tiny alveoli
• with an infolded shape giving a large surface
area
• many branched capillaries
• forming a capillary network with large surface
area
10.7
• Human (mammalian) lung:
• maximum concentration difference
• very good blood supply
• bringing deoxygenated blood (from respiring
cells)
• taking away oxygen (to tissues)
• bringing CO2 from respiring cells
10.7
• Human (mammalian) lung:
• maximum concentration difference
• Ventilation (= breathing)
• bringing fresh atmospheric oxygen-rich air
• bringing fresh atmospheric air with little CO2
• taking away CO2
10.7
• Human (mammalian) lung:
• minimum thickness of gas exchange surface
• capillaries close to the alveolar epithelium
• distance between blood and air down to less
than 1m thick
10.7
• squamous epithelium of alveolus
• 1 cell thick
• very thin, flat cells
• squamous endothelium of capillary
• 1 cell thick
• very thin flat cells
10.7
a = alveoli
b = bronchiole
c = arteriole
d = venule
e = larger
bronchiole
10.7
Alveoli
Bronchiole
10.7
Alveolus
Nucleus of epithelial
cell of alveolus
Capillary
Nucleus of
endothelial cell of
capillary
Macrophage
containing bacteria
10.7
A = alveolus
EP1 = epithelium of
alveolus
EN = endothelium of
capillary
RBC = red blood cell
10.7
• Gross anatomy of respiratory system
Rib
Trachea
Bronchus
Lung
Diaphragm
Larynx (voice box)
Internal intercostal
muscle
External intercostal
muscle
Bronchiole
10.7
• Ventilation
• Inhalation - breathing in
• diaphragm muscle contracts
• diaphragm moves down
10.7
• Ventilation
• Inhalation - breathing in
• diaphragm moves down
• external intercostal
muscles contract
• ribs lifted
• Ventilation
10.7
• Inhalation - breathing in
• diaphragm moves down
• external intercostal
muscles contract
• ribs lifted
• chest volume increased
• pressure in chest drops
• air rushes into chest
10.7
• Exhalation
• diaphragm relaxes and springs back to its
normal curved shape
• elastic fibres in walls of alveoli store energy
during inhalation to make chest spring back
during exhalation
• Internal intercostal muscles contract and pull
ribs down
• Chest volume decreases
• Pressure in chest increases
• Air rushes out
10.7
• In and out tidal breathing
Stretch receptors in chest
Breathing control centre in medulla of brain
Phrenic motor nerves
10.7
• To change from inhalation to exhalation
• Stretch receptors in lung and chest wall are
stretched by inhalation
• Sensory nerves stimulate breathing control
centre in medulla of brain
• Impulses pass down phrenic nerves to
internal intercostals, making you exhale
10.7
• To change from exhalation to inhalation
• Stretch receptors in lung and chest wall are
not stretched by exhalation
• Sensory nerves reduce stimulation of
breathing control centre in medulla of brain
• Impulses pass down phrenic nerves to
external intercostals and diaphragm, making
you inhale
10.7
• Gas
•
•
•
•
O2
CO2
H2O
N2
% in inspired air % in expired air
21
0.04
1
78
15
4
6
75
10.7
• Oxygen % down - diffuses into blood
• Carbon dioxide % up - diffuses out of blood
• Water vapour % up - lost by the wet surface
of the alveoli
• Nitrogen % down only because of the
increase in water vapour
• (actual amount of nitrogen remain constant
as humans cannot use nitrogen gas)
10.8
• Spirometer used to measure lung capacities
• Vital capacity is total volume that can be
breathed in
• Tidal volume is amount that is normally
breathed in
• Can also measure breathing rate and rate of
oxygen consumption
10.8
A spirometer trace
Breathing rate
Resting
tidal
volume
Tidal volume during
exercise
Rate of oxygen
consumption
Time
Exercise starts
10.8
• Pulmonary ventilation = volume of air
breathed in during one minute
• tidal volume = volume breathed in during
one breath in dm3
• breathing rate = number of complete breaths
in one minute in breaths min-1
• Pulmonary ventilation in dm3 min-1
• = tidal volume x breathing rate
10.7 circulation
• General pattern of circulatory system
• Blood vessels entering heart - veins (in to heart)
• inferior and superior vena cava - deoxygenated
blood from tissues - into right atrium
• pulmonary veins - oxygenated blood from lungs into left atrium
• Blood vessels leaving heart - arteries (away
from heart)
• aorta - oxygenated blood to tissues - out of left
ventricle
• pulmonary artery - deoxygenated blood to lungs out of right ventricle
10.7 circulation
• Blood vessels of lung
• pulmonary arteries - deoxygenated blood from
heart - into lungs
• pulmonary veins - oxygenated blood from
lungs - into heart
• Blood vessels of kidney
• renal arteries - oxygenated blood with urea into
kidneys - from heart
• renal veins - filtered, deoxygenated blood away
from kidney - to heart
10.7 circulation
• Blood vessels of liver
• hepatic artery - oxygenated blood into liver,
away from heart
• hepatic portal vein - blood direct from
alimentary canal (intestine) so that nutrients and
toxins can be dealt with by the liver
• hepatic artery - deoxygenated blood from liver
towards the heart
10.7 circulation
Carotid artery
head
Aorta
Pulmonary artery
Superior vena cava
lungs
Hepatic
vein
heart
liver
Hepatic portal vein
Renal vein
kidney
Pulmonary vein
Hepatic artery
gut
Renal artery
Aorta
Inferior vena cava
10.7 circulation
• Capillaries
• 5-10 m diameter
• very many
• very large surface area for exchange
•
•
•
•
single cell thick endothelium
very thin squamous (flat) cells
small thickness of exchange surface
Ref. Fick’s Law
10.7 circulation
Low
hydrostatic
pressure
High
hydrostatic
pressure
artery
High protein - low
water potential
capillary
Low protein - high
water potential
vein
Lymph system drains
excess tissue fluid
Osmosis due to difference in water potential
Movement of small molecules due to hydrostatic
pressure differences
10.7 circulation
• Key features of the formation of tissue fluid
• The net hydrostatic pressure (hp) acting
outwards is the difference between the hp in
the capillary and the hp in the tissue fluid
• net hp = hp in – hp out
• The net water potential () acting outwards
is the difference between the  in the
capillary and the  in the tissue fluid
• net  =  in –  out
• filtration pressure (fp) = water potential ()
+ hydrostatic pressure (hp)
10.7 circulation
= -1kPa
= -1kPa
hp = +1kPa
hp = +1kPa
= -3kPa
hp = +6kPa
artery
capillary
vein
= -3kPa
hp = +2kPa
 in = -3 - -1 = -2kPa
 in = -3 - -1 = -2kPa
hp out = +6 - +1 = +5kPa
hp out = +2 - +1 = +1kPa
fp = +5 + -2 = +3kPa out
fp = +1 + -2 = -1kPa in
10.8 heart
Pulmonary artery
Aorta
Semilunar valves
Vena cava
Right atrium
Tricuspid valve
Right ventricle
Pulmonary vein
Left atrium
Bicuspid valve
(mitral valve)
Left ventricle
10.8 heart
Pulmonary artery
Superior vena cava
Aorta
Semilunar valves
Pulmonary vein
Inferior vena cava
Right atrium
Tricuspid valve
Right ventricle
Left atrium
Bicuspid valve
(mitral valve)
Left ventricle
10.8 heart
Deoxygenated
blood from upper
body tissues
Oxygenated blood to body tissues
Deoxygenated blood to lungs
Oxygenated blood
from lungs
Deoxygenated
blood from
lower body
tissues
10.8 Diastole - myocardium relaxed
Deoxygenated
blood from upper
body tissues
Heart muscle
relaxed
Oxygenated
blood from Heart fills with
blood
lungs
Lasts 0.3 seconds
Deoxygenated
blood from
lower body
tissues
Bicuspid and
tricuspid valves
open
Semilunar valves
shut
10.8 Atrial systole
Artria contract
ventricles remain
relaxed
Topping up the
ventricles with
blood
Lasts 0.1 seconds
Bicuspid and
tricuspid valves
remain open
Semilunar valves
remain shut
10.8 Ventricular systole
Ventricles contract,
atria relax
Empties ventricles
into arteries, atria
refill
Lasts 0.2 seconds
bicuspid and
tricuspid valves
slammed shut
Semilunar valves
open
10.8 Initiation of heart beat
• Muscle cells contract when depolarised
• calcium ion channels open
• calcium ions rush in
• and the muscle cells contract
• Muscle cell are polarised at rest
• calcium ions (Ca2+) actively transported out
• calcium ion gates closed so no diffusion in
10.8 Initiation of heart beat
• The sinoatrial node depolarises
myogenically
• an impulse (wave of depolarisation) spreads
rapidly across the atria
• causing atrial systole (contraction)
• the impulse can’t reach the ventricles due to
a ring of fibrous tissue
• except through the atrioventricular node and
bundle of His
10.8 Initiation of heart beat
• The impulse passes slowly through the
atrioventricular node
• to give the atria time to empty into the
ventricles
• the impulse passes swiftly to the bottom of the
heart in the bundle of His (Purkinje tissue)
• where it spreads over the ventricles
• causing ventricular systole from the bottom up
• so the ventricles empty into the arteries at the
top of the heart
10.8 Initiation of heartbeat
Sinoatrial node
Atrioventricular node
Ring of fibrous
tissue
Bundle of His
10.8 Initiation of heartbeat
Sinoatrial
node
Atrioventricular
node
Fibrous tissue
Bicuspid valve
Bundle of His
Semilunar valves
10.8 Control of heart output
• Hormones e.g adrenaline speeds up heart
rate and makes stroke volume bigger
• Nerves - autonomic nervous system
• sympathetic nerve speeds heart rate up
• parasympathetic (vagus) nerve slows it down
• Stretched cardiac muscle has bigger
contractions - increases stroke volume
10.8 Nervous control of heart rate
• During exercise pressure in vena cava rises
• stretch receptors in the vena cava are
stimulated
• more impulses pass along sensory nerves
• to the cardiac accelerator centre in the
medulla of the brain
• that sends out more impulses in sympathetic
nerves to the sinoatrial node
• speeding up the heart rate
10.8 Nervous control of heart rate
Cardiac accelerator centre in
medulla stimulated, causing
more impulses in sympathetic
nerve to sinoatrial node
More impulses in
sympathetic nerve to
sinoatrial node speeds up
heart rate
Sensory nerves to
medulla in brain carry
more impulses
Stretch receptors in vena
cava are stimulated
More active muscles squeeze
harder and more often on veins
One-way valves in
veins ensure that
blood can only
flow back to heart
10.8 Nervous control of heart rate
• ‘Blood pressure’ is pressure in the arteries
• It rises and falls depending on
• heart rate
• vasoconstriction of arteries
• It can rise too high if:
•
•
•
•
Peak pressure during
systole ‘systolic bp’
120
80
exercise has finished
Minimum pressure
you lie down
during diastole
‘diastolic’ bp)
many arteries vasoconstrict
many arteries lose their elasticity (causes
hypertension = high blood pressure)
10.8 Nervous control of heart rate
•
•
•
•
If pressure in aorta rises dangerously
stretch receptors in the aorta are stimulated
more impulses pass along sensory nerves
to the cardiac decelerator centre in the
medulla of the brain
• that sends out more impulses in
parasympathetic (vagus) nerves to the
sinoatrial node
• slowing down the heart rate
10.8 Nervous control of heart rate
Cardiac decelerator centre in
medulla stimulated, causing
more impulses in
parasympathetic nerve to
sinoatrial node
More impulses in parasympathetic
(vagus) nerve to sinoatrial node slows
down heart rate
Sensory nerves to
medulla in brain carry
more impulses
Stretch
receptors in
aorta and
carotid
arteries
stimulated by
high arterial
blood
pressure
10.8 Pressure and volume in the heart
• During diastole
• pressure is low in atria and ventricles
• volume of ventricles increase
• During atrial systole
• pressure is a bit higher in the atria
• volume of the ventricles continues to increase
• During ventricular systole
• pressure is very high in the ventricles
• ventricular volume drops rapidly
10.8 Pressure and volume in the heart
Semilunar
valves open
Semilunar valves shut
Pressure
Bi & tri
- cuspid
valves
shut
0
Bi & tri - cuspid
valves open
0.2
0.4
0.6
0.8
1.0
Aorta
Volume
Ventricles
Atria
0
0.2
0.4
0.6
0.8
1.0
10.8 Exercise & pulmonary ventilation
•
•
•
•
exercise - muscle works harder
muscle respires more
produces more carbon dioxide
lowers blood pH
• lower blood pH
• increases pulmonary ventilation
10.8 Exercise & cardiac output
• exercise - muscle works harder
• muscle squeezes harder / more often on
veins, pushing blood back to heart faster
• increases venous return of blood to heart
• stretches vena cava and cardiac muscle
• stretched vena cava and cardiac muscle
• increases cardiac output
10.8 Control of cardiac output
• Hormonal
• e.g adrenaline speeds up heart rate and makes
stroke volume bigger increasing cardiac output
• Nervous - autonomic nervous system
• sympathetic nerve speeds heart rate up
• parasympathetic (vagus) nerve slows it down
• Stretching of cardiac muscle
• gives bigger contractions - increases stroke
volume
10.8 Nervous control of heart rate
• During exercise pressure in vena cava rises
• stretch receptors in the vena cava are
stimulated
• more impulses pass along sensory nerves
• to the cardiac accelerator centre in the
medulla of the brain
• that sends out more impulses in sympathetic
nerves to the sinoatrial node
• speeding up the heart rate
10.8 Nervous control of heart rate
Cardiac decelerator centre in
medulla stimulated, causing
more impulses in
parasympathetic nerve to
sinoatrial node
More impulses in parasympathetic
(vagus) nerve to sinoatrial node slows
down heart rate
Sensory nerves to
medulla in brain carry
more impulses
Stretch
receptors in
aorta and
carotid
arteries
stimulated by
high arterial
blood
pressure
10.8 Breathing and exercise
•
•
•
•
•
•
•
•
Muscles respire faster during exercise
more CO2 in blood
lowers blood pH
detected by CO2 receptors in carotid arteries
stimulates respiratory centre in medulla
so you breath more frequently
and tidal volume increases
Pulmonary ventilation increases during
exercise
10.8 Breathing and exercise
Breathing centres in medulla
stimulated and initiate faster
deeper breaths
Intercostal
and
diaphragm
muscles
contract
more often
and more
vigorously
Sensory nerves carry more
impulses
Motor nerves
carry more
impulses
More CO2
in blood,
so pH
lower
(more
acid)
Carotid and
aortic bodies
detect drop in
blood pH
Pulmonary ventilation
Pulmonary ventilation
10.8 Breathing and exercise
CO2
normal
O2
Drop in blood pH due
to increased CO2
causes pulmonary
ventilation to increase
normal
10.6 Tissues
• A tissue is:
• a group of similar cells
• carrying out a similar function
• e.g. epithelium of alveolus in lung
• e.g. blood
10.6 Tissues
•
•
•
•
Epithelial tissues
lining of organs
e.g. squamous epithelium lining lungs
thin flattened cells to:
• minimise diffusion distance and
• maximise rate of diffusion
• ref. Fick’s Law
10.6 Tissues
• Histology of lung
Red blood
cell
Air inside alveolus
Thin
endothelium of
capillary wall
Thin epithelium of
alveolus
10.6 Tissues
• Cuboidal epithelium
• lining kidney tubules
Lumen - hole down middle
Microvilli - to maximise
surface area for diffusion and
active transport
Cuboidal epithelium with lots
of mitochondria to release
energy for active transport
10.6 Tissues
• Columnar epithelium
• e.g. lining trachea
air
Columnar cells
protecting surface of
trachea, with lots of
mitochondria to release
energy for cilia
Cilia to remove mucus
with trapped dust and
bacteria
10.6 Tissues
• Some simple epithelia are one cell thick
• Other stratified epithelia have several layers
of cells
• e.g. skin - stratified squamous epithelium
10.6 Tissues
• Histology of blood
Granulocyte
• ingest bacteria
Erythrocyte - red blood cell
Monocyte
• transports oxygen
• shows antigens to lymphocytes
Lymphocyte
• specific immunity - antibodies
10.6 Tissues
• Red blood cells
• large surface area:volume ratio
• due to biconcave disc shape
• small size so short diffusion distance to centre
• no nucleus
• maximises volume available for carrying
oxygen
• flexible
• so can fit through small capillaries
10.6 Tissues
• As size of a cell increases, e.g. by 2 m
• its volume increases by the cube of the
increase in size, e.g. by 23 m3 = 8 m3
• but its surface area increases only by the
square of the increase in size, e.g. 22 m2 =
2
4 m
• Small cells have larger surface area:volume
ratio
10.6 Tissues
• Find the surface area, volume and surface
area: volume ratio of the following shapes.
The first has been done for you:
Side
1cm
2cm
4cm
8cm
Volume =1x1x1=1cm3
surface area=1x1x6=6cm2
Surface area:volume ratio = sa/vol = 6/1 = 6
10.6 Organs
• Organs
• structures made of different tissues
• co-operating to perform particular functions
• e.g. arteries, arterioles, veins and venules
10.6 Organs
• Artery
lumen - hole down middle
endothelium - covering
tissue like squamous
epithelium
tough connective tissue
with collagen fibres
elastic connective tissue and
smooth muscle tissue
tough connective tissue
with collagen fibres
10.6 Organs
• Aterioles
• small arteries
• with muscle tissue so they can vasoconstrict
- make lumen smaller and vasodilate - allow
lumen to become larger
• and elastic connective tissue - to absorb
pulse
• and strong collagen connective tissue to
resist bursting
10.6 Organs
• Veins
• relatively thin walls mostly of tough
connective tissue with collagen to resist
bursting
• valves to enhance blood flow back to heart
10.6 Organs
• Veins
• large lumen - slow flow - low pressure
• minimises friction
• smooth endothelium lining - minimises friction
and blood clot formation
• thin walls (compared to arteries)
• collagen connective tissue - strong, resist
bursting
• few elastic and muscle fibres - no pulse to
absorb, can’t vasoconstrict
• one-way valves - assist venous return to heart
by preventing backflow of blood
10.6 Organs
A
A
A
B
Skeletal
muscles
relaxed
B
Skeletal
muscles
contract
B
Skeletal
muscles
relaxed